Google imports CSV files, which are easy enough to generate from the Stars spreadsheet. But there doesn't seem to be any way to specify recurring events. So I could import a week at a time, or copy events arbitrarily far in the future and then be in even worse shape when Stars changes things again.
Google also provides a Web API, including a Java library to talk to it. But that seems too much work at the moment. Perl would be about the right amount of effort...
...and, of course, there's a module in CPAN that will talk to Google Calendar. So maybe that's the way to go.
Or I could ask PokerStars support to do it. ;)